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33-hour closure of I-405 in Renton this weekend to congest region's traffic

The state and its contractors were using Friday to stage equipment for the demolition this weekend of the old Benson Road bridge in Renton, seen in the background, over Interstate 405. The new Benson bridge opened recently.

The closure of Interstate 405 in Renton this weekend will have ripple effects for travelers throughout the region.

The closure is needed so that state crews can demolish and haul away a bridge that carried the Benson Road over the freeway near Renton City Hall.

The bridge's removal is part of a nearly $84 million state project to widen the freeway and add an offramp and onramp to serve Talbot Road and downtown Renton.

A new Benson Road bridge opened recently to traffic. The Benson Road will remain open during the demolition of the old bridge.

The freeway closure will stretch from State Route 167 or the Valley freeway to SR 169 or the Maple Valley Highway, starting at 2 a.m. Saturday.

The freeway is expected to reopen by 11 a.m. Sunday, when all the demolished bridge is expected to be hauled away. That's in time for the Return to Renton Car Show, which is expected to attract thousands of visitors to downtown Renton and several hundred cars and trucks.

About 95 percent of the bridge material, including concrete, wood and steel, will be recycled.

The freeway closure is similar to one in 2008 when the state demolished the Wilburton Tunnel on I-405 as part of major freeway improvements in the Bellevue area. The state is spending is spending 10s of millions of dollars to relieve I-405 congestion between Tukwila and Bellevue.

The Stage 2 project when done, perhaps this fall, is the last 405 project in the Renton area until additional money is available for other freeway projects the state is considering.

To prepare for the closure, state officials are asking that thousands of regional travelers divert away from the Renton area. About 145,000 vehicles use the freeway in Renton daily; the state hopes that 100,000 of those will detour around Renton.

The suggested detour is using Interstate 5 to go north or if southbound on I-405, cutting over to I-5 using Interstate 90 to continue going south.

The state will run the I-5 express lanes in the northbound direction and the I-90 express lanes in the westbound direction throughout the 33-hour closure.

Traffic engineers with the state Department of Transportation are predicting congestion WSDOT traffic engineers predict congestion on SR 167, SR 169, I-405, I-5 and I-90 as drivers use these freeways as detours.

They suggest that travelers leave early for a destination or avoid unnecessary trips this weekend. Travel is suggested before 9 a.m. and after 10 p.m. on Saturday to avoid the worst congestion.

The state is expecting heavy congestion on southbound I-5 between Shoreline and Seattle in the afternoon and early evening on Saturday as drivers head downtown for Mariners and the Sounders games because the southbound I-5 express lanes will not be available.

Those who don't detour can navigate around the closure through downtown Renton using specific detour routes. Traffic signals will be timed to help speed traffic through those streets. Additional police will help with traffic control.

“We know this is an inconvenience to drivers, but we need all lanes closed to take down this bridge as safely and efficiently as possible,” said Eastside Corridor Director Kim Henry. “We’ve been dismantling the bridge all week from the inside out to get as much work done without closing the freeway, but at this point we have to bring in the removal equipment.”

The demolition contractor will take down the bridge in 4- and 5-foot chunks to that the debris will fit into a dump truck, said Kory Voldman, deputy construction manager for I-405 Corridor Design-Builders.

Workers will use an excavator equipped with claws for the munchers. A heavy-duty jackhammer will be used, too, which will contribute to the noise of the project.

It's estimated the debris will fill between 100 and 150 double-sized dump trucks.

Besides demolishing the bridge, the state's contractors will do additional work on the freeway, including replacing damaged concrete panels, installing signs and working on storm drainage.

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